The Integumentary System The Skin and its Appendages

The Skin Two main components Epidermis Dermis (Hypodermis)

Epidermis Cells of the Epidermis Keratinocytes Melanocytes Dendritic Cells (Langerhans cells)

Epidermis Layers of the Epidermis Thick Skin Thin Skin Stratum Basale Stratum Spinosum Stratum Granulosum Stratum Lucidum Stratum Corneum Thin Skin Absence of Stratum Lucidum

Epidermis Layers of Epidermis Stratum Basale (germinatum) Single row of stem cells 10-25% melanocytes very small amount of tactile cells

Epidermis Layers of the Epidermis Stratum Spinosum several cells thick weblike intermediate filament network melanin granules and dendritic cells present

Epidermis Layers of the Epidermis Stratum Granulosum Keratinization Begins Keratohyaline granules Lamellar granules

Epidermis Layers of the Epidermis Stratum Lucidum Only present in thick skin 2-3 rows of clear, flat, dead keratinocytes

Epidermis Layers of the Epidermis Stratum Corneum anucleate 20-30 cells thick ¾ of epidermis high keratin content thickened, glycoprotein covered plasma membranes loses 50k cells/min

Dermis Composition Connective Tissue proper Rich nerve and vascular supply contains hair follicles, glands, and sensory receptors Layers Papillary Layer Reticular Layer

Dermis Papillary Layer Thin areolar highly vascularized low density (great for phagocytes) Dermal papillae (form friction ridges in thin skin)

Dermis Reticular layer 80% of Dermis dense irregular connective tissue blood vessel network (cutaneous plexus) cleaveage and flexure lines

Appendages of the Skin Hair and Hair Follicles Nails Sweat Glands Eccrine Glands Apocrine Glands Sebaceous (oil) Glands

Appendages of the Skin Hair and Hair Follicles Structure of hair Structure of a hair follicle Types and growth of hair Hair thinning and baldness

Appendages of the skin Structure of a hair (fig 5.5) Regions Produced by hair follicles Conists primarily of dead keratinized cells cells contain hard keratin Regions Shaft Root Concentric Layers Medulla Cortex Cuticle

Appendages of the skin Structure of a Hair Follicle (fig 5.5) Epithelium based Hair bulb Hair follicle receptor Hair papillae Peripheral connective tissue sheath Epithelial root sheath

Appendages of the Skin Types and Growth of Hair Vellus Hair Terminal Hair

Appendages of the Skin Hair Thinning and Baldness Alopecia True Baldness (Male Pattern)

Appendages of the Skin Nails (fig 5.6) Scale-like modification of epidermis hard keratin free edge, nail plate, root nail bed nail matrix nail folds and cuticle

Appendages of the Skin Sweat (Sudoriferous) Glands Eccrine (Merocrine) Sweat Glands Apocrine Sweat Glands

Appendages of the Skin Sebaceous (Oil) Glands Simple branched alvolar glands secrete sebum holocrine type glands secrete into hair follicles and occasionally pores

Skin Functions Protection Chemical Barriers acid mantle Physical Barriers Biological Barriers dendritic cells, macrophages, DNA

Skin Functions Body Temperature Regulation Heat Loss Vaodilation heat loss through sweat evaporation Heat conservation Vasoconstriction

Skin Functions Cutaneous Sensation

Skin Functions Metabolic Functions Produces vitamin D precursor disarm cancer causing chemicals activate some steroid hormones

Skin Functions Blood Resevoir 5% of total blood volume

Skin Functions Excretion ammonia, uric acid, urea, salt, water.

Homeostatic Imbalances of Skin Skin Cancer Basal Cell Carcinoma Squamous Cell Carcinoma Melanoma Asymmetry Border Irregularity Color Diameter Elevation

Study Guide Will Post Wednesday